Batch and continuous flow studies of Cr(VI) adsorption from synthetic and real wastewater by magnetic pine cone composite

Magnetic pinecone (MNP-PCP) was synthesised via co-precipitation of Fe2+/Fe3+ onto different masses of pine to determine effect of magnetite to pine cone ratio on the Cr(VI) removal capacity. Interaction between magnetite and pine was determined using FTIR, TGA and TEM spectroscopy while iron oxide phase, possible bonding and magnetic properties were confirmed using XRD, XPS and VSM analysis. The composite with 1.5 g of pine removed more Cr(VI) at all solution pH's applied and pH 3 being optimum at which Fe(III) leached into solution was less than 0.01 mg/L. The Langmuir monolayer capacity was observed to be 15.24 mg/g at 26 degrees C while Dubinin-Radushkevish free energy ranged from 15.80 to 16.80 kJ/mol suggesting ligand-ion exchange mechanism. Dynamic studies were done using breakthrough curve to evaluate concentration effect of Cr(VI) adsorption. Thomas model best described the dynamic behaviour while desorption studies showed that four adsorption-desorption and regeneration cycles were possible with an elution efficiency >87% and only 15% loss of capacity after four cycles. Performance of MNP-PCP for real wastewater was comparable with synthetic wastewater. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.